This program is directed at the Research and Development of a high energy density bipolar Nickel- Metal Hydride to serve as the internal power supply for a ventricular assist device. The battery should store enough energy for 45 minutes of operation in order give the recipient maximum portability. It should be as small and lightweight as possible with a life of five years. Rechargeable Ni-MH cells are presently available only as monopolar spirally wound cylindrical cells. Prismatic packs of these cells contain intercell voids. The proposed bipolar Ni-MH system has the potential of being less than one-half the size of present technology NiCd batteries, the only presently viable battery system. In addition the Ni-MH system offers safe operation and employs abundant and environmentally benign materials. Based on the bipolar concept and past activities, this program is directed at the development of an advanced bipolar configuration of the Ni-MH system to maximize volumetric energy density. The ultimate goal is to develop a battery that delivers greater than 70 Wh/kg , 238 Wh/liter, a life of 5 years (1,826 cycles) at 75 DOD and is compatible with implantable systems.